U.S. patent application number 10/327712 was filed with the patent office on 2004-03-11 for modular method for chemical mechanical planarization.
This patent application is currently assigned to Strasbaugh. Invention is credited to Halley, David G..
Application Number | 20040048550 10/327712 |
Document ID | / |
Family ID | 32710799 |
Filed Date | 2004-03-11 |
United States Patent
Application |
20040048550 |
Kind Code |
A1 |
Halley, David G. |
March 11, 2004 |
Modular method for chemical mechanical planarization
Abstract
Specific embodiments of the present invention are directed to a
method of operating a modular chemical mechanical planarization
process. The method comprises operating CMP apparatus comprising a
docking station having at least one CMP module and at least one
cleaning module to process one or more substrates therein. The
plurality of modules are controllable separately by individual
controllers associated separately with the modules. One of the
modules is disengaged from the docking station, and is mechanically
removed to free the module from the docking station, while the
other modules are still operable to process the one or more
substrates therein.
Inventors: |
Halley, David G.; (Los Osos,
CA) |
Correspondence
Address: |
Townsend and Townsend and Crew LLP
8th Floor
Two Embarcadero Center
San Francisco
CA
94111
US
|
Assignee: |
Strasbaugh
San Luis Obispo
CA
|
Family ID: |
32710799 |
Appl. No.: |
10/327712 |
Filed: |
December 19, 2002 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10327712 |
Dec 19, 2002 |
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09699286 |
Oct 26, 2000 |
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60161705 |
Oct 27, 1999 |
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60161830 |
Oct 27, 1999 |
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60161778 |
Oct 27, 1999 |
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Current U.S.
Class: |
451/5 |
Current CPC
Class: |
B24B 37/04 20130101;
B24B 37/30 20130101; H01L 21/67219 20130101; H01L 21/67173
20130101; B24B 37/042 20130101; B24B 37/013 20130101; B24B 49/12
20130101; B24B 57/02 20130101; B24B 49/02 20130101; B24B 9/065
20130101; B24B 53/017 20130101; B24B 37/345 20130101; H01L 21/67167
20130101 |
Class at
Publication: |
451/005 |
International
Class: |
B24B 051/00 |
Claims
What is claimed is:
1. A method of operating a modular chemical mechanical
planarization process, the method comprising: operating a CMP
apparatus comprising a docking station including a plurality of
modules having at least one CMP module and at least one cleaning
module to process one or more substrates therein, the plurality of
modules being controllable separately by individual controllers
associated separately with the modules; disengaging one of the
modules from the docking station; and mechanically removing the one
disengaged module to free the module from the docking station,
while the other modules are still operable to process the one or
more substrates therein.
2. The method of claim 1 wherein the disengaging comprises removing
power and control signals from the docking station.
3. The method of claim 1 wherein the disengaging comprises removing
an exhaust port, a water line, and a plurality of chemical fluid
lines from the docking station.
4. The method of claim 1 further comprising inserting a replacement
module into the docking station and engaging the module for
operation with the docking station while the other modules are
still operable to process the one or more substrates therein.
5. The method of claim 1 wherein the disengaging and mechanically
removing take less than five minutes.
6. The method of claim 1 wherein the cleaning station also dries
the object.
7. The method of claim 1 wherein the plurality of modules are
arranged on a first side of a substrate handling mechanism
configured to transfer substrates between modules.
8. The method of claim 7 wherein a plurality of wafer storage units
are arranged on a second side of the substrate handling mechanism
opposite from the first side.
9. The method of claim 7 wherein the plurality of modules are
linearly arranged on the first side of the substrate handling
mechanism.
10. The method of claim 1 wherein the plurality of modules comprise
at least one CMP module and at least one cleaning module arranged
on a first side, and at least one CMP module and at least one
cleaning module arranged on a second side opposite from the first
side, of a substrate handling mechanism configured to transfer
substrates between modules.
11. The method of claim 10 wherein the plurality of modules are
arranged in a cluster around a substrate handling mechanism
configured to transfer substrates between modules.
12. The method of claim 1 wherein operating the CMP apparatus
comprises polishing a surface of a substrate in a CMP module using
a polishing pad which is substantially smaller in surface area than
the substrate.
13. A method of operating a modular chemical mechanical
planarization process, the method comprising: operating a CMP
apparatus comprising a docking station including a plurality of
modules having at least one CMP module and at least one cleaning
module to process one or more substrates therein; controlling the
plurality of modules separately by individual controllers to
process one or more substrates therein; and disengaging one of the
modules from the docking station, while the other modules are still
operable to process the one or more substrates therein.
14. The method of claim 13 wherein the disengaging comprises
removing power and control signals from the docking station.
15. The method of claim 13 further comprising inserting a
replacement module into the docking station and engaging the module
for operation with the docking station while the other modules are
still operable to process the one or more substrates therein, the
replacement module having an individual controller associated with
the replacement module separate from the controllers for the
modules of the docking station.
16. The method of claim 15 further comprising prequalifying the
replacement module using the individual controller associated with
the replacement module to process one or more substrates therein
for a preset process prior to inserting the replacement module into
the docking station and engaging the module for operation with the
docking station.
17. The method of claim 16 wherein prequalifying the replacement
module comprises processing one or more substrates therein for the
preset process separately from the docking station; and verifying
that the replacement module meets preset minimum performance
requirements based on process results of the one or more substrates
processed therein.
18. The method of claim 13 wherein controlling the plurality of
modules separately comprises controlling separately at least one of
temperature, pressure, polish force, process timing, spindle and
wafer chuck speeds, chemical and D.I. water flow, endpoint
detection set points, and automated sequencing and timing of the
modules.
19. A method of operating a modular chemical mechanical
planarization process, the method comprising: providing a plurality
of modules having at least one CMP module and at least one cleaning
module to process one or more substrates therein, the plurality of
modules being controllable separately by individual controllers to
process the one or more substrates therein; prequalifying at least
one of the plurality of modules separately each for a preset
process associated therewith using the individual controller
associated with the at least one module; coupling the plurality of
modules including the at least one prequalified module with a
docking station of a CMP apparatus; and operating the CMP apparatus
to process one or more substrates in the plurality of modules.
20. The method of claim 19 further comprising disengaging one of
the modules from the docking station, while the other modules are
still operable to process the one or more substrates therein.
21. The method of claim 19 wherein prequalifying the at least one
module comprises processing one or more substrates therein for the
preset process associated therewith separately from the docking
station; and verifying that the at least one module meets preset
minimum performance requirements based on process results of the
one or more substrates processed therein.
Description
[0001] The present application is a continuation-in-part of U.S.
patent application Ser. No. 09/699,286, which is based on and
claims the benefit of U.S. Provisional Patent Application Nos.
60/161,705, 60/161,830, and 60/161,778 filed Oct. 27, 1999. The
entire disclosures of these applications are incorporated herein by
reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the manufacture of
electronic devices. More particularly, the invention provides a
device for planarizing a film of material of an article such as a
semiconductor wafer. In an exemplary embodiment, the present
invention provides an improved substrate support for the
manufacture of semiconductor integrated circuits. However, it will
be recognized that the invention has a wider range of
applicability; it can also be applied to flat panel displays, hard
disks, raw wafers, MEMS wafers, and other objects that require a
high degree of planarity.
[0003] The fabrication of integrated circuit devices often begins
by producing semiconductor wafers cut from an ingot of single
crystal silicon which is formed by pulling a seed from a silicon
melt rotating in a crucible. The ingot is then sliced into
individual wafers using a diamond cutting blade. Following the
cutting operation, at least one surface (process surface) of the
wafer is polished to a relatively flat, scratch-free surface. The
polished surface area of the wafer is first subdivided into a
plurality of die locations at which integrated circuits (IC) are
subsequently formed. A series of wafer masking and processing steps
are used to fabricate each IC. Thereafter, the individual dice are
cut or scribed from the wafer and individually packaged and tested
to complete the device manufacture process.
[0004] During IC manufacturing, the various masking and processing
steps typically result in the formation of topographical
irregularities on the wafer surface. For example, topographical
surface irregularities are created after metallization, which
includes a sequence of blanketing the wafer surface with a
conductive metal layer and then etching away unwanted portions of
the blanket metal layer to form a metallization interconnect
pattern on each IC. This problem is exacerbated by the use of
multilevel interconnects.
[0005] A common surface irregularity in a semiconductor wafer is
known as a step. A step is the resulting height differential
between the metal interconnect and the wafer surface where the
metal has been removed. A typical VLSI chip on which a first
metallization layer has been defined may contain several million
steps, and the whole wafer may contain several hundred ICs.
[0006] Consequently, maintaining wafer surface planarity during
fabrication is important. Photolithographic processes are typically
pushed close to the limit of resolution in order to create maximum
circuit density. Typical device geometries call for line widths on
the order of 0.5 .mu.m. Since these geometries are
photolithographically produced, it is important that the wafer
surface be highly planar in order to accurately focus the
illumination radiation at a single plane of focus to achieve
precise imaging over the entire surface of the wafer. A wafer
surface that is not sufficiently planar, will result in structures
that are poorly defined, with the circuits either being
nonfunctional or, at best, exhibiting less than optimum
performance. To alleviate these problems, the wafer is "planarized"
at various points in the process to minimize non-planar topography
and its adverse effects. As additional levels are added to
multilevel-interconnection schemes and circuit features are scaled
to submicron dimensions, the required degree of planarization
increases. As circuit dimensions are reduced, interconnect levels
must be globally planarized to produce a reliable, high density
device. Planarization can be implemented in either the conductor or
the dielectric layers.
[0007] In order to achieve the degree of planarity required to
produce high density integrated circuits, chemical-mechanical
planarization processes ("CMP") are being employed with increasing
frequency. A conventional rotational CMP apparatus includes a wafer
carrier for holding a semiconductor wafer. A soft, resilient pad is
typically placed between the wafer carrier and the wafer, and the
wafer is generally held against the resilient pad by a partial
vacuum. The wafer carrier is designed to be continuously rotated by
a drive motor. In addition, the wafer carrier typically is also
designed for transverse movement. The rotational and transverse
movement is intended to reduce variability in material removal
rates over the surface of the wafer. The apparatus further includes
a rotating platen on which is mounted a polishing pad. The platen
is relatively large in comparison to the wafer, so that during the
CMP process, the wafer may be moved across the surface of the
polishing pad by the wafer carrier. A polishing slurry containing
chemically-reactive solution, in which are suspended abrasive
particles, is deposited through a supply tube onto the surface of
the polishing pad.
[0008] CMP is advantageous because it can be performed in one step,
in contrast to past planarization techniques which are complex,
involving multiple steps. Moreover, CMP has been demonstrated to
maintain high material removal rates of high surface features and
low removal rates of low surface features, thus allowing for
uniform planarization. CMP can also be used to remove different
layers of material and various surface defects. CMP thus can
improve the quality and reliability of the ICs formed on the
wafer.
[0009] Chemical-mechanical planarization is a well developed
planarization technique. The underlying chemistry and physics of
the method is understood. However, it is commonly accepted that it
still remains very difficult to obtain smooth results near the
center of the wafer. The result is a planarized wafer whose center
region may or may not be suitable for subsequent processing.
Sometimes, therefore, it is not possible to fully utilize the
entire surface of the wafer. This reduces yield and subsequently
increases the per-chip manufacturing cost. Ultimately, the consumer
suffers from higher prices.
[0010] It is therefore desirable to improve the useful surface of a
semiconductor wafer to increase chip yield. What is needed is an
improvement of the CMP technique to improve the degree of global
planarity that can be achieved using CMP.
SUMMARY OF THE INVENTION
[0011] The present invention achieves these benefits in the context
of known process technology and known techniques in the art. The
present invention provides an improved planarization apparatus for
chemical mechanical planarization (CMP). Specifically, the present
invention provides an improved planarization apparatus that
provides multi-action CMP, such as orbital and spin action, to
achieve uniformity during planarization. The present invention
further provides a modular system to reduce footprint and increase
throughput.
[0012] In accordance with an aspect of the present invention, a
method of operating a modular chemical mechanical planarization
process comprises operating a CMP apparatus comprising a docking
station including a plurality of CMP modules having at least one
CMP module and at least one cleaning module to process one or more
substrates therein. The plurality of modules are controllable
separately by individual controllers associated separately with the
modules. One of the modules is disengaged from the docking station,
and is mechanically removed to free the module from the docking
station, while the other modules are still operable to process the
one or more substrates therein. In some embodiments, the
disengaging comprises removing power and control signals from the
docking station. The disengaging may comprise removing an exhaust
port, a water line, and a plurality of chemical fluid lines from
the docking station while the other modules are still operable to
process the one or more substrates therein. The method may further
include inserting a replacement module into the docking station and
engaging the module for operation with the docking station. The
disengaging and mechanically removing take less than five minutes.
The cleaning station also dries the object. The replacement module
may be prequalified by inserting it in a remote prequalification
docking station and engaging the module for prequalification
operation.
[0013] In accordance with another aspect of the invention, a method
of operating a modular chemical mechanical planarization process
comprises operating a CMP apparatus comprising a docking station
including a plurality of modules having at least one CMP module and
at least one cleaning module to process one or more substrates
therein. The plurality of modules are controlled separately by
individual controllers to process one or more substrates therein.
One of the modules is disengaged from the docking station, while
the other modules are still operable to process the one or more
substrates therein.
[0014] In some embodiments, the method further comprises inserting
a replacement module into the docking station and engaging the
module for operation with the docking station while the other
modules are still operable to process the one or more substrates
therein. The replacement module has an individual controller
associated with the replacement module separate from the
controllers for the modules of the docking station. The method may
further comprise prequalifying the replacement module using the
individual controller associated with the replacement module to
process one or more substrates therein for a preset process prior
to inserting the replacement module into the docking station and
engaging the module for operation with the docking station.
Prequalifying the replacement module comprises processing one or
more substrates therein for the preset process separately from the
docking station, and verifying that the replacement module meets
preset minimum performance requirements based on process results of
the one or more substrates processed therein. Controlling the
plurality of modules separately comprises controlling separately at
least one of temperature, pressure, polish force, process timing,
spindle and wafer chuck speeds, chemical and D.I. water flow,
endpoint detection set points, and automated sequencing and timing
of the modules.
[0015] In accordance with another aspect of the present invention,
a method of operating a modular chemical mechanical planarization
process comprises providing a plurality of modules having at least
one CMP module and at least one cleaning module to process one or
more substrates therein. The plurality of modules are controllable
separately by individual controllers to process the one or more
substrates therein. At least one of the plurality of modules is
prequalified separately each for a preset process associated
therewith using the individual controller associated with the at
least one module. The plurality of modules including the at least
one prequalified module are coupled with a docking station of a CMP
apparatus. The CMP apparatus is operated to process one or more
substrates in the plurality of modules.
[0016] In some embodiments, prequalifying the at least one module
comprises processing one or more substrates therein for the preset
process associated therewith separately from the docking station;
and verifying that the at least one module meets preset minimum
performance requirements based on process results of the one or
more substrates processed therein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a simplified diagram of a planarization apparatus
according to an embodiment of the present invention;
[0018] FIG. 1A is a simplified top-view diagram of a carousel for
supporting multiple guide and spin assemblies according to an
embodiment of the present invention;
[0019] FIG. 2 is a detailed diagram of a guide and spin roller
according to an embodiment of the present invention;
[0020] FIG. 2A is a diagram of a guide and spin roller according to
another embodiment of the present invention;
[0021] FIG. 3 is a detailed diagram of a polish pad back support
according to an embodiment of the present invention;
[0022] FIG. 3A is a simplified diagram of a support mechanism for
supporting the wafer with projected gimbal points according to an
embodiment of the present invention;
[0023] FIG. 3B is a top plan view of a gimbal drive support for the
polishing pad with project gimbal point;
[0024] FIG. 3C is a cross-sectional view of the gimbal drive
support of FIG. 3B along 1-1;
[0025] FIG. 3D is a cross-sectional view of the gimbal drive
support of FIG. 3B along 2-2;
[0026] FIG. 3E is an exploded perspective view of the gimbal drive
support of FIG. 3B
[0027] FIG. 4 is a simplified top-view diagram of a planarization
apparatus according to an embodiment of the present invention;
[0028] FIG. 4A is a simplified top-view diagram of the polishing
pad and spindle illustrating spin and orbit rotations;
[0029] FIG. 4B is a sectional view diagram of the orbit and spin
mechanism for the polishing head in accordance with an embodiment
of the present invention;
[0030] FIG. 5 is a simplified diagram of a polishing apparatus
according to an alternative embodiment of the present
invention;
[0031] FIG. 6A is a simplified diagram schematically illustrating
nonuniform polishing using a polishing pad;
[0032] FIG. 6B is a simplified diagram schematically illustrating
the conditioning and shaping of a polishing pad using a dummy
wafer;
[0033] FIG. 6C is a simplified diagram schematically illustrating
the profile of a conditioned polishing pad;
[0034] FIG. 7 is an alternative diagram of a planarization
apparatus according to another embodiment of the present
invention;
[0035] FIG. 8 is a simplified diagram of a planarization apparatus
according to another embodiment of the present invention;
[0036] FIG. 9 is a simplified diagram illustrating a fluid delivery
system in the planarization apparatus of FIG. 8;
[0037] FIG. 10 is a simplified block diagram of a planarization
calibration system of the present invention;
[0038] FIG. 11 is a simplified diagram of a modular system
according to an embodiment of the present invention;
[0039] FIG. 12 is a simplified diagram of a modular system
according to another embodiment of the present invention; and
[0040] FIG. 13 is a simplified diagram of a modular system
according to another embodiment of the present invention.
DESCRIPTION OF THE SPECIFIC EMBODIMENTS
[0041] FIG. 1 is a simplified diagram of a planarization apparatus
100 according to an embodiment of the present invention. This
diagram is merely an example, which should not limit the scope of
the claims herein. One of ordinary skill in the art would recognize
many other variations, modifications, and alternatives. In a
specific embodiment, planarization apparatus 100 is a
chemical-mechanical planarization apparatus.
[0042] Wafer Guide and Spin Assembly
[0043] The apparatus 100 includes an edge support, or a guide and
spin assembly 110, that couples to the edge of an object, or a
wafer 115. While the object in this specific embodiment is a wafer,
the object can be other items such as a in-process wafer, a coated
wafer, a wafer comprising a film, a disk, a panel, etc. Guide
assembly 110 supports and positions wafer 115 during a
planarization process. FIG. 1 also shows a polishing pad assembly
116 having a polishing pad 117, and a back-support 118 attached to
a dual arm 119. Pad assembly 116, back support 117, dual arm 118 is
described in detail below.
[0044] In a specific embodiment, guide assembly 110 includes
rollers 120, each of which couples to the edge of wafer 115 to
secure it in position during planarization. The embodiment of FIG.
1 shows three rollers. The actual number of rollers, however, will
depend on various factors such as the shape and size of each
roller, the shape and size of the wafer, and nature of the
roller-wafer contact, etc. Also, at least one of the rollers 120
drives the wafer 115, that is, cause the wafer to rotate, or spin.
The rest can serve as guides, providing support as the wafer is
polished. The rollers 120 are positioned at various points along
the wafer perimeter. As shown in FIG. 1, the rollers 120 attach to
the wafer 115 at equidistant points along the wafer perimeter. The
rollers 120 can be placed anywhere along the wafer perimeter. The
distance between each roller will depend on the number of rollers,
and on other factors related to the specific application.
[0045] The embodiment of FIG. 1 shows one guide and spin assembly
110. The actual number of such assemblies will depend on the
specific application. For example, FIG. 1A shows a simplified
top-view diagram of a carousel 121 for supporting multiple guide
and spin assemblies 110 for processing multiple wafers 115
according to an embodiment of the present invention. In this
specific embodiment, the carousel (FIG. 1A) can be used with
multiple guide assemblies for planarizing many wafers. The actual
size, shape, and configuration of the carousel will depend on the
specific application. Also, when multiple guide assemblies are
used, all guide assemblies need not be configured identically. The
configuration of each guide assembly will depend on the specific
application. For higher throughput, wafers are mounted onto the
guide assemblies that are in cue during the planarization of one or
more of the other wafers. For even higher throughput, such wafer
carousels are configured to operatively couple to multiple
planarization apparatus.
[0046] FIG. 2 is a detailed diagram of a roller 120 of FIG. 1
according to an embodiment of the present invention. This diagram
is merely an example, which should not limit the scope of the
claims herein. One of ordinary skill in the art would recognize
many other variations, modifications, and alternatives. As shown,
each roller 120 has a base portion 125, a top portion 130, and an
annular notch 131 extending completely around the roller, and
positioned between the base and top portions. The depth and shape
of notch 131 will vary depending on the purpose of the specific
roller. A roller designated to drive the rotation of the wafer
might have a deeper notch to provide for more surface area contact
with the wafer 115. Alternatively, a roller designated to merely
guide the wafer might have a shallower notch, having enough depth
to provide adequate support.
[0047] FIG. 2A shows another roller 120a having a base portion 125a
similar to the base portion 125 of FIG. 2. The top portion 130a has
a smaller cross-section that the top portion 130 of FIG. 2, and
desirably includes a tapered or inclined surface 132a tapering down
to an annular notch 131a which is more shallow than the notch 131
of FIG. 2. The shallow notch 131a is sufficient to connect the
roller 120a to the edge of the wafer 115. The top portion 130a and
the shallow notch 131a make the engagement of the roller 120a with
the edge of the wafer 115 easier. The replacement of the wafer 115
can also be performed more readily and quickly since the roller
120a with the smaller to portion 130a need not be retracted as far
as the roller 120 of FIG. 2. The surface 133a of the bottom portion
125a may also be inclined by a small degree (e.g., about
1-5.degree.) as indicated by the broken line 133b to further
facilitate wafer engagement.
[0048] The edge of wafer 115 is positioned in the notch of each
roller such that the process side of wafer 115 faces polishing pad
117. To secure wafer 115, the base portion of each roller provides
an upward force 140 against the back side 150 of the wafer while
the top portion provides a downward force 160 against the process
surface 170 (side to be polished) of the wafer. For additional
support, the inner wall 171 of the notch provides an inward force
190 against the wafer edge. The top and base portions 130, 125
constitute one piece. Alternatively, the top and base portions 130,
125 can include multiple pieces. For example, the top portion 130
can be a separate piece, such as a screw cap or other fastening
device or the equivalent. Each roller 120 has a center axis 201 and
each can rotate about its axis. Rotation can be clockwise or
counterclockwise. Rotation can also accelerate or decelerate.
[0049] Guide and spin assembly 110 also has a roller base (not
shown) for supporting the rollers. The size, shape, and
configuration of the base will depend on the actual configuration
of the planarization apparatus. For example, the base can be a
simple flat surface that is attached to or integral to the
planarization apparatus. The base can support some of the rollers,
while at least one roller need to be retractable sufficiently to
permit insertion and removal of the wafer 115, and need to be
adjustable relative to the edge of the wafer 115 to control the
force applied to the edge of the wafer 115.
[0050] In operation, during planarization, guide assembly 110 can
move wafer 115 in various ways relative to polishing pad 117. For
example, the guide assembly can move the wafer laterally, or
provide translational displacement, in a fixed plane, the fixed
plane being substantially parallel to a treatment surface of
polishing pad 117 and back support 118. The guide assembly can also
rotate, or spin, the wafer in the fixed plane about the wafer's
axis. As a result, the guide assembly 110 translates the wafer 115
in the x-, y-, and z-directions, or a combination thereof During
actual planarization, that is when a polishing pad contacts the
wafer, the guide assembly can move the wafer laterally in a fixed
plane. The guide assembly can translate the wafer in any number of
predetermined patterns relative to the polishing pad. Such a
predetermined pattern will vary and will depend on the specific
application. For example, the pattern can be substantially radial,
linear, etc. Also, at least when the polishing pad contacts the
object during planarization, such a pattern can be continuous or
discontinuous or a combination thereof.
[0051] Conventional translation mechanisms for x-, y-,
z-translation can control and traverse the guide assembly. For
example, alternative mechanisms include pulley-driven devices and
pneumatically operated mechanisms. The guide assembly and the wafer
can traverse relative to the polishing pad in a variety of
patterns. For example, the traverse path can be radial, linear,
orbital, stepped, etc. or any combination depending on the specific
application. The rotation direction of the wafer can be clockwise
or counter clockwise. The rotation speed can also accelerate or
decelerate.
[0052] Still referring to FIG. 2, as indicated above, in addition
to lateral movement, the guide assembly can also rotate, or spin,
wafer 115 in the fixed plane about the wafer center axis 202. The
fixed plane is substantially parallel to a treatment surface of
polishing pad 117. One way to provide rotational movement is by
using rollers 120 described above. As mentioned above, at least one
roller rotates about its center axis to drive the wafer to rotate
about its center axis. The other rollers can also drive the wafer
to rotate. They can also rotate freely. As said, each roller can
rotate about its center axis 201 in either a clockwise or
counterclockwise direction. The wafer will rotate in the opposite
direction of the driving roller.
[0053] Specifically, as one or more of the driving rollers spin
along their rotational axis 201 during operation, the friction
between the inner walls of notch 131 and the wafer edge cause wafer
115 to rotate along its own axis 202. The roller itself can provide
the friction. For example, the notch can include ribs, ridges,
grooves, etc. Alternatively, a layer of any known material having a
sufficient friction coefficient, such as a rubber or polyamide
material, can also provide friction. One of ordinary skill in the
art would recognize many other variations, modifications, and
alternatives. For example, each roller can be movably or immovably
fixed to a base (not shown) and a wheel within the notch of each
roller can spin, causing the wafer to spin.
[0054] To rotate, or spin, the wafer, one or more conventional
drive motors (not shown) or the equivalent can be operatively
coupled to the wafer, rollers, or roller base. The drive can be
coupled to one or more of the rollers via a conventional drive belt
(not shown) to spin the wafer. Alternatively, the drive can also
couple to the guide assembly such that the entire guide assembly
rotates about its center axis thereby causing the wafer to rotate
about the guide assembly center axis. With all embodiments, the
motor can be reversible such that the rotation direction 275 (FIG.
1) of the polishing pad 117 about its axis 270 can be clockwise or
counter clockwise. Drive motor can also be a variable-speed device
to control the rotational speed of the pad. Also, the rotational
speed of the pad can also accelerate or decelerate depending on the
specific application.
[0055] Alternatively, the edge support can also be stationary
during planarization while a polishing pad rotates or moves
laterally relative to the wafer. This variation is described in
more detail below. During planarization, such movement occurs in
the fixed plane at least when the polishing pad 117 contacts the
wafer. During any part of or during the entire planarization
process, any combination of the movements described above is
possible.
[0056] Referring to FIG. 1, planarization apparatus 100 also
includes a polishing head, or polishing pad assembly 116, for
polishing wafer 115. Pad assembly 116 includes polishing pad 117, a
polishing pad chuck 250 for securing and supporting polishing pad
117, and a polishing pad spindle 260 coupled to chuck 250 for
rotation of pad 117 about its axis 270. According to a specific
embodiment, the pad diameter is substantially less than the wafer
diameter, typically 20% of the wafer diameter.
[0057] To rotate, or spin, the wafer, one or more conventional
drive motors (not shown) or the equivalent can be operatively
coupled to polishing pad spindle 260 via a conventional drive belt
(not shown). The motor can be reversible such that the rotation
direction 275 of polishing pad 117 can be clockwise or counter
clockwise. Drive motor can also be a variable-speed device to
control the rotational speed of the polishing pad. Also, the
rotational speed of the polishing pad can also accelerate or
decelerate depending on the specific application.
[0058] Polishing and Back Support Assembly
[0059] The planarization apparatus also includes a base, or dual
arm 119. While the base can have any number of configurations, the
specific embodiment shown is a dual arm. Pad assembly 116 couples
to back support 118 via dual arm 119. Dual arm 119 has a first arm
310 for supporting pad assembly 116 and a second arm 320 for
supporting back support 118. The arms 310, 320 may be configured to
move together or, more desirably, can move independently. The arms
310, 320 can be moved separately to different stations for changing
pad or puck and facilitate ease of assembling the components for
the polishing operation.
[0060] According to a specific embodiment of the invention, back
support 118 tracks polishing pad 117 to provide support to wafer
115 during planarization. This can be accomplished with the dual
arm. In a specific embodiment, the pad assembly 116 attaches to
first arm 310 and back support 118 attaches to second arm 320. Dual
arm 119 is configured to position the pad assembly 116 and back
support 118 such that a support surface of back support 118 faces
the polishing pad 117 and such that the support surface of back
support 118 and polishing pad 117 are substantially planar to one
another. Also, according to the present invention, the centers of
the polishing pad and surface of the back support are precisely
aligned. This precision alignment allows for predicable and precise
planarization. Precision alignment is ensured when the first and
second arms constitute one piece. Alternatively, both arms can
include multiple components and may be movable independently. As
such, the components are substantially stable such that the
precision alignment is maintained.
[0061] Specifically, according to one embodiment, dual arm 119
supports pad assembly 116 such that spindle 260 passes rotatably
through first arm 310 towards back support 118 which is supported
by second arm 320. The rotational axis 270 of the pad 117 is
equivalent to that of the spindle 260. Rotational axis 270 is
positioned to pass through back support 118, preferably through the
center of the back support 118. Pad assembly 116 is configured for
motion in the direction of wafer 115. FIG. 1 shows the process
surface of the wafer positioned substantially horizontally and
facing upwardly.
[0062] According to a specific embodiment of the present invention,
the entire planarization system can be configured to polish the
wafer in a variety of positions. During planarization, for example,
the dual arm 119 can be positioned such that the wafer 115 is
controllably polished in a horizontal position or a vertical
position, or in any angle. These variations are possible because
the wafer 115 is supported by rollers 120 rather than by gravity.
Such flexibility is useful in, for example, a slurry-less polish
system.
[0063] In operation, dual arm 119 can translate pad assembly 116
relative to wafer 115 in a variety of ways. For example, the dual
arm 119 can pivot about the pivot shaft to traverse the pad 117
radially across the wafer 115. In another embodiment, both arms 310
and 320 can extend telescopically (not shown) to traverse the pad
laterally linearly across the wafer 115. Both radial and linear
movements can also be combined to create a variety of traversal
paths, or patterns, relative to the wafer 115. Such patterns can
be, for example, radial, linear, orbital, stepped, continuous,
discontinuous, or any combination thereof. The actual traverse path
will of course depend on the specific application.
[0064] FIG. 3 is a detailed diagram of back support 118 of FIG. 1
according to an embodiment of the present invention. This diagram
is merely an example, which should not limit the scope of the
claims herein. One of ordinary skill in the art would recognize
many other variations, modifications, and alternatives. Back
support 118 supports wafer 115 during planarization. Specifically,
back support 118 dynamically tracks polishing pad 117 to provide
local support to wafer 115 during planarization. Such local support
eliminates wafer deformation due to the force of the polishing pad
against the wafer during planarization. This also results in
uniform polishing and thus planarity. In a specific embodiment, the
back support 118 operatively couples to the pad assembly 116 via
the dual arm 119. In a specific embodiment, the back support 118 is
removably embedded in second arm 320 of the dual arm. Referring to
FIG. 1, rotational axis 270 of polishing pad 117 and spindle 260
pass through back support 118.
[0065] Referring back to FIG. 3, back support 118 can be configured
in any number of ways for supporting wafer 115 during
planarization. In a specific embodiment, back support 118 has a
flat portion, or support surface 350, that contacts the back side
150 of the wafer during planarization. The support surface 350
desirably provides a substantially friction free interface between
surface 350 and back side 150 of the wafer by using a low-friction
solid material such as Teflon. Alternatively, the support surface
350 may support a fluid bearing as the frictionless interface with
the back side 150. The fluid may be a gas such as air or a liquid
such as water, which may be beneficial for serving the additional
function of cleaning the back side 150 of the wafer. This friction
free interface allows the wafer to move across the surface of the
back Support.
[0066] Support surface 350 is substantially planar with the wafer
115 and pad 117. The diameter of the surface should be large enough
to provide adequate support to the object during planarization. In
a specific embodiment, the back support surface has a diameter that
is substantially the same size as the polishing pad diameter. In
FIG. 3, the back support 118 shown is a spherical air bearing and
has a spherical portion 340 allowing it to be easily inserted into
second arm 320. The rotation of the spherical portion 340 relative
to the second arm allows the back support 118 to track the
polishing pad 117 and support the wafer 115 with the support
surface 350. The back support 118 in FIG. 3 has a protrusion 341
into a cavity of the second arm. The protrusion 341 may serve to
limit the rotation of the back support 118 relative to the second
arm 320 during tracking of the polishing pad 117. In an alternate
embodiment, the back support 118 may be generally hemispherical
without the protrusion.
[0067] The process surface 170 of the wafer 115 faces the pad 117
and the back side 150 of the wafer 115 faces the back support 118.
Also, the wafer 115 is substantially planar with both the pad 117
and back support 118. In another embodiment, the back support 118
can be replaced with a second polishing pad assembly for
double-sided polishing. In such an embodiment, the second pad
assembly can be configured similarly to the first pad assembly on
the first arm. The polishing pads of each are substantially planar
to one another and to the wafer 115.
[0068] In a specific embodiment, the back support is a bearing. In
this specific embodiment, the bearing can be a low-friction solid
material (e.g., Teflon), an air bearing, a liquid bearing, or the
equivalent. The type of bearing will depend on the specific
application and types of bearing available.
[0069] In the specific embodiment as shown in FIG. 1, the dual arm
119 is a C-shaped clamp having projected gimbal points that allow
for flexing of the dual arm 119 and still keep the face of the
wafer in good contact with the polishing pad 117. The projected
gimbal points are more clearly illustrated in FIG. 3A. The
polishing pad chuck 250 is supported by the first arm 310, and the
back support 118 is supported by the second arm 320. The polishing
pad chuck 250 has a hemispherical surface 251 centered about a
pivot point or gimbal point 252 which preferably is disposed at or
near the upper surface of the wafer 115. Positioning the gimbal
point 252 at or near the surface of the wafer 115 allows gimbal
motion or pivoting of the chuck 250 relative to the first arm 310
without the problem of cocking. Cocking occurs when the projected
gimbal point is above the wafer surface, and causes the forward end
of the polishing pad 117 to dig into the wafer surface at the
forward edge and lift up at the rear edge. The cocking is
inherently unstable. Positioning the project gimbal point on the
wafer surface avoids cocking. If the gimbal point is projected
below the surface of the wafer, friction between the polishing pad
117 and the wafer surface produces a skiing effect which lifts the
forward edge of the polishing pad 117 and causes the rear edge to
dig into the wafer surface as the polishing pad moves relative to
the wafer surface. This is more stable than cocking. The desirable
maximum distance between the projected gimbal point and the wafer
surface depends on the size of the polishing pad 117. For example,
the distance may be less than about 0.1 inch for a polishing pad
having a diameter of about 1.5 inch. The distance is desirably less
than about 0.1 times, more desirably less than about 0.02 times,
the diameter of the polishing pad. Likewise, the spherical surface
340 of the back support 118 desirably has a projected pivot point
254 disposed at or near the lower surface of the wafer 115.
[0070] FIGS. 3B-3E show the gimbal mechanism coupling the polishing
pad chuck 250 with the first arm 310. The chuck 250 is connected to
an inner cup 256 which is connected to an outer cup 258 that is
supported by the first arm 310 of the dual arm 119. A torsional
drive motor may be coupled with the outer cup 258 to rotate the
polishing pad 117 via the gimbal mechanism around the z-axis. A
pair of inner drive pins 262 extend from the chuck 250 into radial
slots 264 provided in the inner cup 256 and extending generally in
the direction of the y-axis. The radial slots 264 constrain the
inner drive pins 262 in the circumferential direction so that the
chuck 250 moves with the inner cup 256 in the circumferential
direction around the z-axis. The inner drive pins 262 may move
along the radial slots 264 to permit rotation of the chuck 250
relative to the inner cup 256 around the x-axis.
[0071] A pair of outer drive pins 266 extend from the inner cup 256
into radial slots 268 provided in the outer cup 258 and extending
generally in the direction of the x-axis. The radial slots 268
constrain the outer drive pins 266 in the circumferential direction
so that the inner cup 256 moves with the outer cup 258 in the
circumferential direction around the z-axis. The outer drive pins
266 may move along the radial slots 268 to permit rotation of the
inner cup 256 relative to the outer cup 258 around the y-axis.
[0072] The hemispherical drive cups 256, 258 isolate two axes of
motion to allow full gimbal of the gimbal mechanism about the
gimbal point or pivot point 252. The gimbal mechanism allows
transmission of the torsional drive of the polishing pad 117 about
the z-axis without inducing a torque moment on the polishing pad
117 at the interface with the wafer surface to produce a skiing
effect. The polishing pad 117 becomes self-aligning with respect to
the surface of the wafer 115 which may be offset from the x-y
plane.
[0073] The gimbal mechanism shown in FIGS. 3B-3E is merely
illustrative. In different embodiments, the drive pins may be
replaced by machined protrusions. Balls or rollers that fit into
mating, crossing grooves may be used to provide rolling contact
with low friction between the movable members of the mechanism.
Although the embodiment shown includes a single track in the
x-direction and a single track in the y-direction, additional
tracks may be provided. The members of the assembly may have other
shapes different from the spherical members and still provide
gimbal movements or spherical drive motions. It is understood that
other ways of supporting the wafer and of tracking the polishing
pad may be employed to provide the projected gimbal point at the
desired location.
[0074] Planarization apparatus 100 operates as follows. Referring
back to FIG. 1, assembly 110 positions wafer 115 between polishing
pad 117 and back support 118. The polishing pad is lowered onto the
process surface 170 of the wafer 115. Pad assembly 116 is driven by
a conventional actuator (not shown), a piston-driven mechanism, for
example, having variable-force control to control the downward
pressure of the pad 117 upon the process surface 170. The actuator
is typically equipped with a force transducer to provide a
downforce measurement that can be readily converted to a pad
pressure reading. Numerous pressure-sensing actuator designs, known
in the relevant engineering arts, can be used.
[0075] FIG. 4 is a simplified top-view diagram of planarization
apparatus 100 according to an embodiment of the present invention.
This diagram is merely an example, which should not limit the scope
of the claims herein. One of ordinary skill in the art would
recognize many other variations, modifications, and alternatives.
In a specific embodiment, dual arm 119 is configured to pivot about
a pivot shaft 360 to provide translational displacement of pad
assembly 116, and polishing pad 117, relative to guide and spin
assembly 110, and wafer 115. Pivot shaft 360 is fixed to a
planarization apparatus system (not shown).
[0076] The polishing pad spindle 260 may also rotate to rotate the
polishing pad 117, as illustrated in FIG. 4A. In addition to the
spin rotation 276 about its own axis 270, the spindle 260 may also
orbit about an orbital axis 277 in directions 278 to produce
orbiting of the polishing pad 117 as shown in broken lines. The
orbital axis 277 is offset from the spin axis 270 by a distance
which may be selected based on the size of the wafer 115 and the
size of the polishing pad 117. For instance, the offset distance
may range from about 0.01 inch to several inches. In a specific
example, the distance is about 0.25 inch. The orbital rotation is
more clearly illustrated in FIG. 4A. Different motors may be used
to drive the spindle 260 in spin and to drive the spindle 260 in
orbital rotation.
[0077] FIG. 4B shows an apparatus 600 that allows both orbital and
pure spin motion of a polishing head 602 that holds a polishing pad
604 which is smaller in size than the wafer 606 for planarizing the
wafer. An orbit housing 610 is held in place with respect to the
arm frame 612 by bearings 614 and driven directly by a direct orbit
motor or through an orbit belt or an orbit gear. FIG. 4B shows an
orbit drive belt 616 coupled to an orbit motor 618. The orbit
housing 610 has an eccentric or offset hole 620 which supports a
shaft 622 with bearings 624. The shaft 622 is offset from the
centerline of the orbit housing 610 by an offset 625 which may be
set to any desired amount (e.g., about 0.5 inch). The shaft 622 is
connected to the polishing head 602. An external tooth gear 626 (or
friction drive or the like) is attached to the shaft 622 and mates
with an internal tooth gear 628 (or friction drive). The internal
tooth gear is a ring gear 628 supported by another bearing 630
concentric with the outer orbit housing bearings 614, and is driven
by a direct spin motor, or through a spin gear or a shaft drive
belt. FIG. 4B shows a spin drive belt 632 coupled to a spin motor
634. By controlling the relative speeds of the orbit motor 618 and
the spin motor 634, the polishing head 602 can be made to spin only
(while holding the orbit motor 634 stationary), to spin and orbit
(i.e., to precess), or to orbit only (by controlling the relative
motions of the two motors 618, 634 so that the polishing pad 604
does not spin relative to the wafer 606). FIG. 4B also shows a
chemical/fluid/slurry supply 640 supplying the
chemical/fluid/slurry through a feed passage 642 to the polishing
pad 604.
[0078] The inventors have discovered that improved uniformity of
planarization can be achieved by polishing the center of the wafer
by predominately orbital motion and polishing the edge of the wafer
by predominately spin motion. Predominate orbital motion at the
center of the wafer produces relatively uniform surface velocity
motion to the entire polish pad surface where the center of the
wafer is at a theoretical zero velocity. This results in good
uniformity at the center of the wafer while maintaining superior
planarity. Pure spin motion allows a very precise balance position
at the edge of the wafer to give superior edge exclusion polish
results where the orbital motion causes the pad to tend to drop off
the edge too far before the center of action can be close enough to
the edge to achieve good removal. This produces good uniformity
results at the edge of the wafer while maintaining superior
planarity results. In some embodiments, the orbiting speed is
greater than the spinning speed when the polishing pad is contacted
with the center region of the wafer. In a specific embodiment, the
spinning speed is approximately zero at the center region. In some
embodiments, the spinning speed is greater than the orbiting speed
when the polishing pad is contacted with an edge region of the
wafer. In a specific embodiment, the orbiting speed is
approximately zero at the edge region.
[0079] The inventors have also found that uniformity can be
affected by the relative wafer rotational speed and orbiting speed
of the polishing pad. For instance, during combined orbital motion
and rotation of the wafer, if the ratio of the greater of the
orbiting speed and the wafer rotational speed to the lesser of the
two is an integer, then the polishing pattern will repeat in a
Rosette pattern and produces nonuniformity polishing. Typically,
the orbiting speed is larger than the wafer rotational speed. Thus,
it is desirable to have the ratio of the two speeds be a
non-integer to achieve improved uniformity during planarization.
For example, if the orbiting speed is 1000 rpm, the wafer
rotational speed may be 63 rpm.
[0080] FIG. 5 is a simplified top view diagram 500 of a multi-pad
CMP apparatus according to an embodiment of the present invention.
This diagram is merely example, which should not limit the scope of
the claims herein. One of ordinary skill in the art would
recognizes many other variations, modifications, and alternatives.
As shown, the diagram 500 illustrates a top-view of a base panel
501, which houses a variety of systems and sub-systems. The base
panel 501 is a frame support structure, which has doors for
enclosing the frame support structure.
[0081] The panel includes a polishing head 515 (or arm), which
pivots about member 517. The polishing head extends from member 517
to a region overlying the object 507 to be polished. The object can
be a variety of work pieces, such as a semiconductor wafer, a glass
plate, a flat panel, a blank wafer, a disk, and other objects with
surfaces that need polishing or planarization. The object often
rests on and is attached to a base plate or platen 505. The base
plate can often rotate the object in either direction.
Additionally, the base plate can ramp up in speed, or step up in
speed, or perform other functions.
[0082] The polishing head includes a polishing pad 19, which is
coupled to the polishing head. The polishing pad rotates in a
circular or orbital manner and traverses across the surface of the
object. The polishing pad can also move in the vertical direction
to a selected height. Other functions of the polishing pad have
been previously noted and also apply here, but should not unduly
limit this embodiment.
[0083] The polishing pad can move from the object to one of a
plurality of sites. These sites include a disposal site 502, where
the polishing pad can be removed. The disposal site can also
include a device, such as the handling arms, which are used to
remove the polishing pad and cap from the polishing head. Here, the
polishing arm completes a polishing process, is elevated, and
traverse to the disposal site 502, where the handling arms clamp
the cap, the drive motor turns the drive shaft to free the cap, and
the polishing head lifts up to free itself from the cap. Next, the
arms release the cap, including the pad, into the disposal site. In
a specific embodiment, the disposal site can be covered, when it is
not in use to prevent particulate contamination from being released
from the disposal site to the object.
[0084] Shaping Polishing Pad
[0085] Another aspect of the invention is directed to modifying the
shape of the polishing pad to eliminate or reduce nonuniformity of
the wafer during CMP. As shown in FIG. 6A, the relatively high
downforce applied on the polishing pad 520 by the pad holder 522
tends to deform the wafer 524 into a dish shape during CMP. If the
pad 520 is relatively hard, it will remain substantially planar and
the edge region of the pad 520 will be more likely to make contact
with the wafer surface than the center region of the pad 520. This
contact creates rings on the wafer surface during CMP and causes
planarization non-uniformity. One way to reduce the ring effect is
to use a softer polishing pad material. Alternatively, the
polishing pad can be rotated at a higher spinning or grinding
speed. These solutions may be undesirable.
[0086] One aspect of the invention is to modify a polishing pad
(typically made of a very hard material) by conditioning it in situ
using a wafer and sheet abrasive to generate a profile on the
surface of the pad. The pad profile so formed is more suitable or
optimized for polishing a wafer under the same forces during CMP to
achieve superior planarity and maintain uniformity.
[0087] In one embodiment, a layer of fine sand paper 526 (e.g., 600
G) is bonded to the surface of a dummy wafer or conditioning wafer
528 for use in conditioning a polishing pad 520 prior to the actual
planarization process, as seen in FIG. 6B. The polishing pad 520 is
placed in contact with the sand paper 526 using a downforce and
under conditions similar to the actual planarization process, while
the polishing speeds may be reduced from the speeds during actual
planarization. The sand paper 526 will wear down the polishing pad
520 at the edge region. The polishing pad is checked periodically,
typically at short time intervals (e.g., about 5-10 seconds), until
the beginning of a polish pattern is detected in the center region
of the pad. This signals that the desired polishing pad shape is
achieved for use in the actual planarization process. In general,
the desired shape of the polishing pad 520' has a substantially
flat center region and a rounded edge region, as shown in FIG. 6C.
This can be observed by holding a precision rule 530 against the
surface and observing the flatness of the center region.
Over-conditioning the pad is undesirable by eliminating the flat
center region and destroying planarity. Of course, other abrasive
material can be used instead of the sand paper.
[0088] After conditioning the polishing pad 520', the sand paper is
flushed to remove particles thereon. The polishing pad 520' is
cleaned and the dummy wafer 528 is removed. The same apparatus may
be cleaned and used for actual planarization, or a different
apparatus may be employed to planarize a wafer using the
conditioned polishing pad 520'.
[0089] In another embodiment, the shape of the conditioned
polishing pad 520' can be used to preform polishing pads having the
same profile to be used for CMP under the same conditions. The pads
may be preformed by molding. In this way, the shaping of the
polishing pad 520' only needs to be performed once for the
particular CMP application.
[0090] Polishing Chemical Delivery
[0091] FIG. 7 is an alternative diagram of planarization apparatus
100 according to another embodiment of the present invention. This
diagram is merely an example, which should not limit the scope of
the claims herein. One of ordinary skill in the art would recognize
many other variations, modifications, and alternatives. In a
specific embodiment, a slurry delivery mechanism 400 is provided to
dispense a polishing slurry (not shown) onto the process surface of
wafer 115 during planarization. Although FIG. 7 shows a single
mechanism 400 or dispenser 400, additional dispensers may be
provided depending on the polishing requirements of the wafer.
Polishing slurries are known in the art. For example, typical
slurries include a mixture of colloidal silica or dispersed alumina
in an alkaline solution such as KOH, NH.sub.4OH or CeO.sub.2.
Alternatively, slurry-less pad systems can be used.
[0092] A splash shield 410 is provided to catch the polishing
fluids and to protect the surrounding equipment from the caustic
properties of any slurry that might be used during planarization.
The shield material can be polypropylene or stainless steel, or
some other stable compound that is resistant to the corrosive
nature of polishing fluids. The slurry can be dispose via a drain
420.
[0093] A controller 430 in communication with a data store 440
issues various control signals 450 to the foregoing-described
components of the planarization apparatus. The controller provides
the sequencing control and manipulation signals to the mechanics to
effectuate a planarization operation. The data store 440 can be
externally accessible. This permits user-supplied data to be loaded
into the data store 440 to provide the planarization apparatus with
the parameters for planarization. This aspect of the invention will
be further discussed below.
[0094] Any of a variety of controller configurations is
contemplated for the present invention. The particular
configuration will depend on considerations such as throughput
requirements, available footprint for the apparatus, system
features other than those specific to the invention, implementation
costs, and the like. In a specific embodiment, controller 430 is a
personal computer loaded with control software. The personal
computer includes various interface circuits to each component of
apparatus 100. The control software communicates with these
components via the interface circuits to control apparatus 100
during planarization. In this embodiment, data store 440 can be an
internal hard drive containing desired planarization parameters.
User-supplied parameters can be keyed in manually via a keyboard
(not shown). Alternatively, the data store 440 is a floppy drive in
which case the parameters can be determined elsewhere, stored on a
floppy disk, and carried over to the personal computer. In yet
another alternative, the data store 440 is a remote disk server
accessed over a local area network. In still yet another
alternative, the data store 440 is a remote computer accessed over
the Internet; for example, by way of the world wide web, via an FTP
(file transfer protocol) site, and so on.
[0095] In another embodiment, controller 430 includes one or more
microcontrollers that cooperate to perform a planarization sequence
in accordance with the invention. Data store 440 serves as a source
of externally provided data to the microcontrollers so they can
perform the polish in accordance with user-supplied planarization
parameters. It should be apparent that numerous configurations for
providing user-supplied planarization parameters are possible.
Similarly, it should be clear that numerous approaches for
controlling the constituent components of the planarization
apparatus are possible.
[0096] FIG. 8 shows a CMP apparatus 700 disposed in a process
cavity 702. A wafer 704 is transported into the process cavity 702
using a robot end effector (edge grip) 706 and supported on a wafer
platen 708 which may be a vacuum chuck made of a porous material. A
splash shield 710 is desirably placed around the wafer and platen
708. The wafer platen 708 is supported on a rotary shaft 712 which
is coupled with a vacuum rotary union 714. A wafer drive motor 716
is connected to the rotary shaft 712 to spin the shaft 712, platen
708, and wafer 704.
[0097] A polishing chuck 720 is disposed above the wafer 704 and
supported on an arm 722. The arm 722 is housed in an arm cover 724
and supported on an arm support pivot tube 726 which has a hollow
center through which a slurry chemical supply tube 730 extends for
supplying a slurry chemical to the polishing chuck 720. A spindle
drive motor 734 drives a spindle coupled to the polishing chuck 720
to rotate around its axis to spin the polishing pad over the wafer
surface. The pivot tube 726 is rotatable relative to the frame 736
and is mounted to the frame by a bearing assembly 738. An arm
rotation drive assembly and motor unit 740 rotates the arm 722
through the arm support tube 726 around the axis of the tube 726.
An arm lift assembly and drive unit 742 is provided to move the arm
722 up and down through the arm support tube 726. An auto change
pad magazine 750 may be provided for supplying polishing pads which
are detachably connected to the polishing chuck 720 for polishing
the wafer 704. A cavity spray rinse/wash 756 is disposed on top of
the apparatus 700 with a splash containment cover 758 surrounding
the upper portion to reduce splashing.
[0098] FIG. 9 shows additional details of the delivery of the
slurry chemical. A pump 760 pumps the slurry chemical from a source
762 through the supply tube 730 to a hollow spindle shaft 764
connected to the polishing chuck 720. The chemical flows through
the channel 766 in the spindle shaft 764 and the polishing chuck
720 under gravity, and into the region between the annular
polishing pad 770 and the surface of the wafer 704. The center
application of the chemical through a removed center portion of the
polishing pad 770 advantageously produces uniform chemical
distribution even at high spindle speeds, thereby minimizing
chemical consumption. The use of a slurry-less pad 770 eliminates
the problem of slurry build-up in the spindle 764. A non-contact
level sensor 774 is desirably provided to monitor the chemical
level in the channel 766 of the shaft 764 to ensure proper chemical
flow. The sensor information can be used to control the pump 760
via a pump controller 776 to adjust the pumping to achieve the
desired chemical flow rate and level and avoid flow interruption.
FIG. 9 further shows a belt and pulley coupling 780 between the
spindle drive motor 734 and the spindle shaft 764. The wafer
holding vacuum for the vacuum chuck 708 is generated by using a
high velocity air (or water or other fluids) flow away from the
opening 784 at the bottom of the wafer chuck shaft 712. This may
employ a non-contact vacuum venturi 786 with compressed air flow
788 for increased reliability.
[0099] Planarization Calibration System
[0100] FIG. 10 is a simplified block diagram of a planarization
calibration system of the present invention. It is noted that the
figure is merely a simplified block diagram representation
highlighting the components of the planarization apparatus of the
present invention. The system shown is exemplary and should not
unduly limit the scope of the claims herein. A person of ordinary
skill in the relevant arts will recognize many variations,
alternatives and modifications without departing from the scope and
spirit of the invention. Planarization system 800 includes a
planarization station 804 for performing planarization operations.
Planarization station 804 can use a network interface card (not
shown) to interface with other system components, such as a wafer
supply, measurement station, transport device, etc. There is a
wafer supply 802 for providing blank test wafers and for providing
production wafers. A measurement station 806 is provided for making
surface measurements from which the removal profiles are generated.
The planarization station 804, wafer supply 802 and measurement
station 806 are operatively coupled together by a robotic transport
device 808. A controller 810 includes control lines and data input
lines 814 that cooperatively couple together the constituent
components of system 800. Controller 810 includes a data store 812
for storing at least certain user-supplied planarization
parameters. Alternatively, data store 812 can be a remotely
accessed data server available over a network in a local area
network.
[0101] Controller 810 can be a self-contained controller having a
user interface to allow a technician to interact with and control
the components of system 800. For example, controller 810 can be a
PC-type computer having contained therein one or more software
modules for communicating with and controlling the elements of
system 800. Data store 812 can be a hard drive coupled over a
communication path 820, such as a data bus, for data exchange with
controller 810.
[0102] In another configuration, a central controller (not shown)
accesses controller 810 over communication path 820. Such a
configuration might be found in a fabrication facility where a
centralized controller is responsible for a variety of such
controllers. Communication path 820 might be the physical layer of
a local area network. As can be seen, any of a number of controller
configurations is contemplated in practicing the invention. The
specific embodiment will depend on considerations such as the needs
of the end-user, system requirements, system costs, and the
like.
[0103] The system diagrammed in FIG. 10 can be operated in
production mode or in calibration mode. During a production run,
wafer supply 802 contains production wafers. During a calibration
run, wafer supply 802 is loaded with test wafers. Measurement
station 806 is used primarily during a calibration run to perform
measurements on polished test wafers to produce removal profiles.
However, measurement station 806 can also be used to monitor the
quality of the polish operation during production runs to monitor
process changes over time.
[0104] In another embodiment, measurement system 806 can be
integrated into planarization station 804. This arrangement
provides in situ measurement of the planarization process. As the
planarization progresses, measurements can be taken. These real
time measurements allow for fine-tuning of the planarization
parameters to provide higher degrees of uniform removal of the film
material.
[0105] The program code constituting the control software can be
expressed in any of a number of ways. The C programming language is
a commonly used language because many compilers exist for
translating the high-level instructions of a C program to the
corresponding machine language of the specific hardware being used.
For example, some of the software may reside in a PC based
processor. Other software may be resident in the underlying
controlling hardware of the individual stations, e.g.,
planarization station 804 and measurement station 806. In such
cases, the C programs would be compiled down to the machine
language of the microcontrollers used in those stations. In one
specific embodiment, the system employs a PC-based local or
distributed control scheme with soft logic programming control.
[0106] As an alternative to the C programming language,
object-oriented programming languages can be used. For example, C++
is a common object-oriented programming language. The selection of
a specific programming language can be made without departing from
the scope and spirit of the present invention. Rather, the
selection of a particular programming language is typically
dependent on the availability of a compiler for the target
hardware, the availability of related software development tools,
and on the preferences of the software development team.
[0107] Modular CMP System
[0108] FIGS. 11 and 12 show examples of modular CMP systems. The
modular system 1100 in FIG. 11 includes 4 process modules P, 1
cleaning module C, 1 wafer handling member or robot R, 4 wafer
storage units W, and 2 metrology modules M in an arrangement that
reduces footprint and increases throughput. FIG. 12 shows another
modular system 1200 including 6 process modules P, 2 cleaning
modules C, 2 wafer handling members or robots R.sub.1, R.sub.2, 4
wafer storage units W, and 1 metrology module M. The modular system
1100 is a relatively shallow configuration with a bulkhead 1102,
while the module system 1200 is a relatively deep configuration
with a bulkhead 1202. An operative interface panel 1106 is disposed
with the wafer storage units W on one side of the bulkhead 1102
having automated guided vehicle (AGV) access in FIG. 11. Similarly,
an operative interface panel 1206 is disposed with the wafer
storage units W on one side of the bulkhead 1202 in FIG. 12.
[0109] FIG. 11 illustrates withdrawal 1110 of the cleaning module C
for maintenance or replacement. FIG. 12 illustrates withdrawal 1210
of a process module P for maintenance or replacement. The plug-in
configuration of the modules provides interchangeability of the
modules while continuing operation with the other modules. During
module removal, the fluid line, communication/electrical line,
interlocks, and the like are disconnected and reconnected.
Different configurations can be created with identical modules. The
modular configuration allows one to select a configuration that
best suits its needs, and provides flexibility in the number of
types of modules used as well as the space required. The module
size can range from a small system (e.g., 1 process, 1 clean, 1
robot, and 1 foup for full dry in/dry out capability in a very
small footprint for development work) to a large system with
multiple process modules, cleaning modules, robots, and foups. It
is possible to form a double-ended system by adding a mirror image
of the modules on the other side of the symmetry line 1220. With a
double ended system, it is conceivable to have up to 4 cleaning
modules, 16 or 20 process modules, and 8 or 10 foups per
configuration. The modular system may further be expanded, for
instance, by stacking the modules. FIG. 13 shows an alternative
modular system 1300 having modules in a cluster arrangement with
all the modules facing a polar type robot R with angular spaces
therebetween.
[0110] In some embodiments, the plurality of modules in the modular
system 1100 are controlled separately by individual controllers to
process one or more substrates therein. Each module can operate
autonomously and separately from the other modules. This is one way
to allow one of the modules to be conveniently disengaged from the
docking station of the modular system 1100, while the other modules
are still operable to process the one or more substrates therein.
The individual controller may include, for example, components for
controlling temperature, pressure, polish force, process timing,
spindle and wafer chuck speeds, chemical and D.I. water flow,
endpoint detection set points, automated sequencing and timing, or
the like.
[0111] When it is desirable to remove one module and replace it
with a replacement module, the replacement module may be
prequalified offline prior to inserting the replacement module into
the docking station and engaging the module for operation with the
docking station. The replacement module has an individual
controller associated with the replacement module separate from the
controllers for the other modules. The replacement module can be
prequalified using the individual controller associated with the
replacement module to process one or more substrates therein for a
preset process, such as a specific CMP process or cleaning process.
Prequalifying the replacement module may include processing one or
more substrates therein for the preset process separately from the
docking station, and verifying that the replacement module meets
preset minimum performance requirements based on process results of
the one or more substrates processed therein. For a CMP process,
the preset minimum performance requirements may include a minimum
level of planarization, dishing and erosion, removal rates, site
total thickness variation (TTV), process pad life, automated puck
handling performance, sensor set point levels, surface roughness,
or the like. For a cleaning process, the preset minimum performance
requirements may include number of defects, residue and/or
particles left after the cleaning process, or the like.
[0112] The modules may also be individually prequalified offline
prior to coupling them to the docking station of the modular system
1100. This distributed control scheme for the modules using their
own separate controllers renders the modular system 1100 more
flexible and robust.
[0113] The modular system may further employ input and output tools
such as the standard mechanical interface system (SMIF.TM.)
available from Asyst Technologies. An SMIF-Pod.TM. provides
contamination control during transport and storage by isolating the
wafer cassettes from the ambient environment, and maintains and
controls cleanliness essentially independent of the external room
environment.
[0114] While the above is a full description of the specific
embodiments, various modifications, alternative constructions and
equivalents known to those of ordinary skill in the relevant arts
may be used. For example, while the description above is in terms
of a semiconductor wafer, it would be possible to implement the
present invention with almost any type of article having a surface
or the like. Therefore, the above description and illustrations
should not be taken as limiting the scope of the present invention
which is defined by the appended claims.
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